This invention relates to a power supply device for generating at least one output voltage from an input voltage having an absolute value higher than that of the output voltage and by means of a DC/DC converter which comprises a primary circuit and a secondary circuit.
Power supply devices comprising DC/DC converters supplying one or more output voltages are required for the powering of electronic apparatus. Among clocked DC/DC converters notably the basic types flyback converter and forward converter can be distinguished. Therein, via a controllable switch an input DC voltage is converted into a squarewave voltage which is rectified and smoothed.
European patent 27 171-A1 describes a power supply device comprising a DC/DC converter which is constructed as a forward converter as shown in FIG. 2 of this patent. The DC/DC converter comprises a primary circuit which includes an input capacitor to which an input voltage can be applied. Parallel to the input capacitor there is connected a primary winding of a transformer in series circuit with the switching path of a controllable switch which is constructed as a transistor and which can be controlled by a control circuit at the secondary side of the converter. This series includes an output capacitor. The secondary side includes a secondary winding of the transformer in series with a rectifier diode and the output capacitor across which an output voltage can be derived.